Selection pressures operate on populations in such a way as to increase the overall fitness of a population. An example of this can be seen in the birth weights of human babies. For humans, giving birth is a special, but often traumatic, event. In a study of human birth weights, it is possible to observe the effect of selection pressures on a population. For humans, if an infant is born weighing 1kg, just 20% survive. If the birth weight increases just 1⁄2 kg (1.5kg), then the survival rate is 70%. As birth weight increases to 2.0kg, survival rate is 88% and it is 96% at 2.5kg. Both 3kg and 4kg have a survival rate of 97%, while the survival rate is 98% for 3.5kg babies. At 4.5kg the survival rate decreases to 93% and it is 85% for 5kg babies. Fill in the data table below and graph the information using the appropriate graph.